1. Field of the Invention
This invention relates broadly to dental implants. More particularly, this invention relates to dissection and elevation of the subantral membrane of the maxillary sinus for osseous regeneration in order to increase the bony support structure for a dental implant.
2. State of the Art
Dental implants have been used in dentistry for about 20 years. They offer a tremendous benefit to patients by allowing the replacement of missing teeth. The success of a dental implant is based on a variety of factors including: surgical technique, health of the patient, operator skill and, to a significant part, sufficient bone for the placement and integration of the dental implant. To that end, dental implants are commonly used in the anterior lower jaw, as this region provides sufficient bone quantity, quality and strength to support and hold the dental implant. However, the replacement of the maxillary teeth have presented a considerable challenge because after the loss of maxillary teeth the quality and quantity of the remaining supporting bone may be insufficient to properly and reliably support the dental implant.
More particularly, the maxillary complex is a three-dimensional bone structure composed of alveolar bone and basal bone. The maxillary teeth, and more specifically the teeth roots, are imbedded in the alveolar bone. The top of the maxillary complex forms the floor of the maxillary sinus and is covered by a thin diaphanous membrane known as the subantral or Schneiderian membrane (referred to herein as the “subantral membrane”). Once a tooth is removed from the maxillary complex, the surrounding alveolar bone is frequently resorbed because of the lack of physical stimulation and support of the teeth. This leads to a loss of bone mass and a corresponding reduction in the effective height and thickness of the bone of the maxillary complex, which if not remedied limits the potential use of the dental implant.
To overcome the deficiency of insufficient vertical bone mass of the maxillary complex, several surgical techniques have been developed to increase available bone mass for the placement of dental implants. These techniques augment the bone deficient region with a filler or regenerative material made of natural and/or artificial (synthetic) materials. Such material is placed on the roof of the maxillary structure under the subantral membrane so that it does not interfere with the function of the maxillary sinus. Collectively, these procedures are known within the dental profession as “sinus elevation procedures” with the goal of increasing the vertical height available for placement of dental implants. What makes these techniques unique from other techniques, such as distraction osteogenesis, is that the bone is increased within a body cavity, i.e., the maxillary sinus cavity.
Bone augmentation of the maxillary sinus requires delicate dissection of the subantral membrane from the floor of the sinus. If the membrane is not properly dissected from the bone, bone augmentation may not occur, or may not be sufficient. Unintentional perforation of the subantral membrane may also lead to undesirable short and long-term consequences. If the perforation is large, for example, several millimeters in diameter, the surgeon must either abort the procedure or must use some means of removing or containing the regenerative material on the floor of the sinus to encourage new bone growth. Typically, a collagen membrane patch is used to repair the perforation and contain the regenerative material on the floor of the sinus. A lack of integrity of the membrane can also lead to the migration of regenerative bone materials leading to long-term chronic infections. Therefore, the maintenance of membrane integrity is of utmost importance during the elevation of the membrane to allow placement of regenerative materials with a goal of increasing bone mass in the maxilla.
A commonplace sinus elevation procedure requires a window into the maxillary sinus from a lateral and superior approach to the floor of the sinus. Great care must be taken during the entry to the sinus as it is critical not to perforate the subantral membrane that lines the sinus cavity. Most patients and dental surgeons acknowledge that entrance into the maxillary sinus utilizing a lateral window approach (also known as the Caldwell-Luc procedure) is an invasive procedure. This technique is fraught with many risks and complications because of the limitations of healing potential in the maxillary sinus. In spite of these risks many patients undergo this procedure because of the strong desire to replace missing maxillary teeth with dental implants.
An alternative procedure described by Dr. R. B. Summers approaches the maxillary sinus from the alveolar ridge utilizing solid cylindrical osteotomes. It is a more conservative approach and is less invasive. The technique vertically lifts the subantral membrane from the floor of the maxillary sinus via an infracture of the bony floor. Regenerative material is placed into this space for bone augmentation. The bone regenerative materials are actually used to raise the subantral membrane. The infracture can be performed using solid cylindrical osteotomes with specific diameters that are vertically advanced toward the maxillary sinus producing a mechanical lifting action on the membrane. The technique has a variety of shortcomings as well, including limitations in the ability to carefully dissect (or separate) the subantral membrane from the floor of the sinus. While this technique is safer, an overzealous use of an osteotome during the procedure can result in the perforation of the subantral membrane with disadvantages discussed above.
Several other sinus elevation procedures have also been introduced. One such procedure uses a medical syringe to inject fluid that raises the subantral membrane from the floor of the maxillary sinus. Another technique uses a catheter balloon placed under the subantral membrane in order to raise the subantral membrane from the floor of the maxillary sinus. This procedure requires an infracture of the underlying bone similar to the Summer procedure or a lateral window approach previously described. An additional technique described by Dr. Leon Chen called “Hydraulic Sinus Condensing” drills a small hole in the crest of the alveolar ridge. A steam of water under hydraulic pressure is delivered to the hole, which loosens the sinus membrane. A small window is made on the lateral crest and bone graft material mixed with plasma rich protein is condensed under the loosened sinus membrane. As more and more bone is grafted and condensed, the sinus membrane is elevated. U.S. Patent Application No. 2006/0084034 describes the use of a sleeve that is inserted through the alveolar ridge to the maxillary sinus in order to raise the subantral membrane and form a cavity. In the process, the sleeve can also cut and/or condense bone around itself.
In all of these prior art techniques, tearing or ripping of the subantral membrane may still occur. Such tearing or ripping is also difficult to detect while raising the subantral membrane. Such deficiencies and limitations relate primarily to the inability to carefully separate the membrane from its physical adherence to the floor of the maxillary sinus. Overcoming these previous limitations in the technique of sinus elevation will reduce infection, bleeding, swelling, pain, suffering and failure when using dental implants in the maxillary sinus.